Telephonic transmission-circuit.



H. G. DOHSEY.; TELEPHONIC TRANSMISSION CIRCUIH;

' APPLICATION FILED SEPT-7. 19:2.

' j Patepgdnly 13,1915.

particularly tov a circuit including a tele,

HERBERT Gr. DORSEY, EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF NEW'YORK, N. Y., A. CORPORATION 0E ILLINOIS.

TLEPHONIC 'TRANSMISSION-CIRCUIT.

Specification of Letters Patent." Patented Illy 13, 1915.

l Application filed September?, 1312. Serial No. 719,208.

To all whom 1f-may concern vBe it known that I, HERBERT G. DoRsEY, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented a certain new and useful Improvement y in Telephonic Transmission-Circuits, of which the following 'is a full, clear, concise, and exact de-I scription. l

This invention relates to improvements 1n a telephonie transmisslon circuit and-more phonic relay or repeater for linking two talking circuits together for the purposeof reinforcing or renewing the currents employed in telcphonic transmission. l

The object of this invention is to provide improved means for eliminating or reducing to. a great extent the tendency of the telephonie relay to produce disturbing noises, on the vline due to the mutual action of the receiver yand transmitter elements commonly called singing, without perceptibly affecting the quality or volume given by the repeater. This disturbance or singing is due to-various causes, onebeing the character of unbalance in the tvvolinked circuits, anotherand probably the predominating cause being inherent qualitiesv of the repeater vwhich determine the prominent peak of the energy factor curve; that is the highest point of a curve obtained by plotting the frequency of the input currents in pulsations per second against the energy factor which is the ratio of the output energy inthe transmitter. to the 'input energy in the receiving coil.

In accordance with this invention means are provided for decreasing the energy factor at the frequency of singing by means of a connection, including apparatus for offer| ing lessfimpedance to the telephonie currents transmitted at or about the singing frequency of the telephonie relay, thus reducing the energy factor at this frequency to a very low value. This connection contains an inductance, a capacity and resistance,- either or all of which may be madel variable, and may beconnected either around the receiving element, the transmitter but ton or the repeating coil, the first arrangement being the preferable one. By varying the relation of the resistance'inductance and capacity the impedance of the circuit containing them is varied. y

ln the drawing illustrating this invention,

connecting the 'main line conductors. transmitter 7 of said .relay apparatus 5 1s mediate station C. The station C divides the line intol two sections or links and has located thereat a current reinforcing message'repeating or relay apparatus 5 comprising a receiving element 6 in a bridge included in a local circuit containing the primary Winding 8 of an induction coil 9 and a battery or like source of electrical energy 10. The secondary winding of the coil 9 iselectrically divided into four sections 11, l2, 13 and 14, these sections being connected in pairs' upon opposite sides of the bridge containing the receiving element 6. Connected in shunt of the receiving element 6 in Fig. 1 is a condenser 20 and an inductive resistance 2l having an adjustable core 22, the movement of which; varies the frequencyof resonance of the shunt circuit. When connected in this manner the devices shunt the incorging energy. v

In Fig. 2, th'e'""pparatus is shown as connected around. the transmitter element 7 in .which relation the generated energy is denser 20 and inductive resistance are connected around the primary winding 8 of the induction 9 and shuntthe outgoing en ergy. j

ln Fig. 4 are shown two energy factor curves taken with a repeater, the transmitter element of which is :provided with a vibrating member having a naturally high frequency. The. solid line Vcurve gives the values of the energy factor at different frequencies of a repeater without the resonant shunt and the'dotted line curve gives thevalues of the energy factor at different frequencies of the same repeater with the shunt applied/thereto. its' will be noted from these curves the energy factor of the repeater reaches a maximum at a frequency of about 2200 and 2400 pulsations per second, whereas with the shunt applied thereto this 10 2200 pulsations per second will not appre- *I lfenergy factor is'reduced to acomparatively lowzv'alue atabout thesame frequency. In-

asmuch as' the tendencyof the repeater to e sing is normally at. the highest value of the f" `'energy factor, this tendencywill be overcome 1f `means are' provided` for reducing the energy factor at the singing frequency -andthis is done by means of the shunt las hereinbefore described. The-low energy fac` tor atv the particular frequencyv of about I ciably affecttransmission as it has been disvfactor can lbe Vreduced covered' that very little telephonie transmission takes place at this frequency- By vary- 5 -15 'ngfthe'capacity and inductance the energy to any desired 'fre'- quency and to almost any desired '.degree,

I thus providing for the elimination ofrsingl currents a v vingre'peaters of different characteristics.

Lil-The combination With av telephone cir,-

v 1' cuit'yof a'telephonic relay associatedtherewithyand- -means for rendering-Isaidgrelay j ,relatively less capable of amfplfying currentsiharing ralperiod of said relaythan-l of amplifying currents of other frequencies.

frequency equal to, 'the natu- 2. The'combination with a telephone cirlcuigof'a telephohic relay associated therewith,and' an auxiliary circuit for rendering said relay relatively less capable of amplifyfrequency equal to the Vmy name this 30th day of August A. D 1912. I

natural period of said relay than of ampli- .fying currents of other frequencies. .v 3 3. The'combination with a telephone .circuit, of a telephonic relay associated therewith, a shunt circuit for said relay and apparatus in Asaid shunt circuit rendering it .resonant to currents having a frequency equal to the natural frequency of the said relay.

4. The combination -With a telephone cirin said circuit rendering it resonant to currents of a ,frequency equal to the natural frequency of s aid relay.

cuit, of a telephonic relay having a highv natural frequency 'associated'therewith a shunt circuit .for said relay and apparatus -5. The combination with a telephone circuit, of a telephonie relay having ajnatural 50v 'frequency above normal maXinuJrn r telephonic frequencies associated with, said circuit,- a shunt for said relay and apparatus in said shunt 4rendering it resonant to frequencies above normal' maximum telephonie frequencies. r

In witness whereof,` I hereunto subscribe 

